diff --git a/internal/client_channel.go b/internal/client_channel.go
index 57791b7..e82a434 100644
--- a/internal/client_channel.go
+++ b/internal/client_channel.go
@@ -201,7 +201,7 @@ func (t *TClient) getExtByFilenameAndMimeType(filename, mimeType string) string
 	if filename != "" && strings.Contains(filename, ".") {
 		ext = filepath.Ext(filename)
 		if ext != "" {
-			return ext
+			return strings.ToLower(ext)
 		}
 	}
 
diff --git a/main_test.go b/main_test.go
index e15fd3c..e5da021 100644
--- a/main_test.go
+++ b/main_test.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"mime"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"exporter/database/telegram_resource/public/table"
@@ -83,11 +84,34 @@ func Test_PublishGrpc(t *testing.T) {
 }
 
 func Test_Ext(t *testing.T) {
-	name := "abc.jpg"
-	ext := filepath.Ext(name)
-	t.Logf("Name: %s, Ext: %s", name, ext)
-
-	name = "abc_jpg"
-	ext = filepath.Ext(name)
+	name := "abc.MOV"
+	mime := "video/quicktime"
+	ext := getExtByFilenameAndMimeType(name, mime)
 	t.Logf("Name: %s, Ext: %s", name, ext)
 }
+
+func getExtByFilenameAndMimeType(filename, mimeType string) string {
+	ext := ""
+	if filename != "" && strings.Contains(filename, ".") {
+		ext = filepath.Ext(filename)
+		if ext != "" {
+			return strings.ToLower(ext)
+		}
+	}
+
+	exts, err := mime.ExtensionsByType(mimeType)
+	if err != nil {
+		return ext
+	}
+
+	if len(exts) == 0 {
+		switch mimeType {
+		case "application/rar":
+			ext = ".rar"
+		}
+	} else {
+		ext = exts[len(exts)-1]
+	}
+
+	return strings.ToLower(ext)
+}